Strip sourcemap comment from REPL JS before diffing and executing

src/repl.ts

@@ -480,6 +480,8 @@ export function createEvalAwarePartialHost(
   return { readFile, fileExists };
 }
 
+const sourcemapCommentRe = /\/\/# ?sourceMappingURL=\S+[\s\r\n]*$/;
+
 type AppendCompileAndEvalInputResult =
   | { containsTopLevelAwait: true; valuePromise: Promise<any> }
   | { containsTopLevelAwait: false; value: any };
@@ -525,8 +527,23 @@ function appendCompileAndEvalInput(options: {
 
   output = adjustUseStrict(output);
 
+  // Note: REPL does not respect sourcemaps!
+  // To properly do that, we'd need to prefix the code we eval -- which comes
+  // from `diffLines` -- with newlines so that it's at the proper line numbers.
+  // Then we'd need to ensure each bit of eval-ed code, if there are multiples,
+  // has the sourcemap appended to it.
+  // We might also need to integrate with our sourcemap hooks' cache; I'm not sure.
+  const outputWithoutSourcemapComment = output.replace(sourcemapCommentRe, '');
+  const oldOutputWithoutSourcemapComment = state.output.replace(
+    sourcemapCommentRe,
+    ''
+  );
+
   // Use `diff` to check for new JavaScript to execute.
-  const changes = diffLines(state.output, output);
+  const changes = diffLines(
+    oldOutputWithoutSourcemapComment,
+    outputWithoutSourcemapComment
+  );
 
   if (isCompletion) {
     undo();

src/test/repl/repl.spec.ts

@@ -32,6 +32,16 @@ test('should run REPL when --interactive passed and stdin is not a TTY', async (
   expect(stdout).toBe('> 123\n' + 'undefined\n' + '> ');
 });
 
+test('should echo a value when using the swc transpiler', async () => {
+  const execPromise = exec(
+    `${CMD_TS_NODE_WITH_PROJECT_FLAG} --interactive  --transpiler ts-node/transpilers/swc-experimental`
+  );
+  execPromise.child.stdin!.end('400\n401\n');
+  const { err, stdout } = await execPromise;
+  expect(err).toBe(null);
+  expect(stdout).toBe('> 400\n>401\n > ');
+});
+
 test('REPL has command to get type information', async () => {
   const execPromise = exec(`${CMD_TS_NODE_WITH_PROJECT_FLAG} --interactive`);
   execPromise.child.stdin!.end('\nconst a = 123\n.type a');